This invention relates to an image transmitting system and an image transmitting method for transmitting image data with high quality over a network line such as a public line or a LAN (local area network) line and an image processing system and an image processing method suitably used for transmitting image data in such a manner and storing high-quality image data. Further, the present invention also relates to color facsimile machines, or to transmission/reception of images of the Internet.
Hitherto, image data has been transmitted and stored increasingly. For example, monochrome binary image data is MR, MMR coded, etc., then transmitted or stored with a machine typified by normal G3, G4 facsimile. Various means such as an orthogonal transformation coding transmission technique typified in the Unexamined Japanese Patent Application Publication No. Sho 63-308474, etc., for example, are also proposed for color images. In either case, basically, an input image is handled as one plane and is compressed, then transmitted or stored.
Processing responsive to the image structure of each part of an image, such as text or picture, is also performed. For example, to transmit binary data (monochrome facsimile image), simple binarization processing is performed for a text part and dither. binarization processing is performed for a picture part, then the resultant binary output is MR or MMR coded, then transmitted.
On the other hand, for color multivalued images typified by photos, the orthogonal transformation coding transmission technique is often used to compress image data. First, an input image is divided into blocks each of a predetermined size, then orthogonal transformation is performed for each block. Quantization processing is performed for the resultant orthogonal transformation output and the result is coded and compressed. However, the following problem is pointed out for the technique: If the technique is applied to text or a line drawing, degradation of mosquito noise, etc., is produced although the technique is effective for picture portions such as photos.
For example, the Unexamined Japanese Patent Application Publication No. Hei 4-354263 discloses a technique, assuming that a text or line drawing part is represented in binary form, for recognizing a binary part (text or line drawing part) and a multivalued part (picture or photo part) contained in an image and MMR coding the binary part and orthogonal transformation coding the multivalued part, then transmitting the result. The receiving party decodes and decompresses the coded and compressed data separately and recombines the decoded and decompressed data. The basic idea is similar to a technique for separating an image into a binary image plane of text and a multivalued image plane of picture or photo according to attribute and handling the planes; a compression technique fitted to text is used for the text image plane and a compression technique fitted to a picture or photo is used for the picture or photo image plane, whereby the compression rate is improved and image degradation is made inconspicuous.
However, with recent image data, text and line drawings have also been represented in multivalued form or color rather than in binary form increasingly. If an image with a mixture of text, a line drawing, and a picture represented in multivalued form or color is attempted to be transmitted using the conventional technique as described above, binary image coding, such as MMR, cannot be applied to text or line drawings, thus text and line drawings cannot be handled as binary parts. As one method to solve the problem, text and line drawings represented in multivalued form are binarized, whereby the conventional technique can be used. However, the quality of text and line drawings is degraded or discoloration occurs.
By the way, text and line drawings tend to become higher image quality as they are of higher resolution. Therefore, it is desirable to transmit or store text or a line drawing at high resolution as much as possible. However, if the resolution is raised haphazardly, the data amount increases and the transmission load also grows. Since text or a line drawing represented in multivalued form or color also has gradation information, the data amount grows more than that of binary data. If a large-capacity line carrying a load is used, no problem arises. However, if a small-capacity line such as a public line is used to transmit a multivalued or color image, it takes too long to transmit the image.
It is therefore an object of the invention to provide an image processing system and an image processing method capable of transmitting or storing image data in the optimum data amount with high image quality and an image transmitting system and an image transmitting method for transmitting image data in such a manner.
In the invention, input image information is converted into the multilayer data format consisting of a first piece of image data, a second piece of image data, and selection data for selecting either the first piece of image data or the second piece of image data. For example, a picture part such as a photo in the input image information can be made the first piece of image data, color information in a text or line drawing part can be made the second piece of image data, and form information in the text or line drawing part can be made the selection data. The selection data, which is used only for selecting either the first piece of image data or the second piece of image data can be handled as binary data and can be compressed at a high compression rate with image quality maintained at high resolution.
To reduce the transmitted or stored data amount, a method of converting high-resolution image data into low-resolution image data and furthermore compressing the data is possible in addition to changing of the compression method in response to the attribute as described above. Particularly, the second piece of image data need not be high resolution and can be converted into low resolution and compressed because the text or line drawing form information is separated.
Thus, in the invention, the input image information is separated into the first piece of image data, the second piece of image data, and the selection data and resolution conversion processing and data compression can be executed in response to the first piece of image data, the second piece of image data, and the selection data, whereby high-quality image data can be transmitted or stored in a small data amount.
To thus execute resolution conversion, it is necessary to balance the data amount and image quality. If it is not considered, transmission time is taken too much or the storage area is occupied unnecessarily because the transmission data amount is too large. In contrast, the transmission time is short and no storage area is required, but satisfactory image quality is not provided in some cases. Thus, in the invention, the resolutions of the first piece of image data, the second piece of image data, and the selection data are preset properly in response to the image characteristics, system characteristics, system limitation, transmission amount limitation, etc., whereby the image data can be transmitted or stored with the optimum image quality in the appropriate data amount.
Setup-resolution image data is provided by scanning an original image through the input means in accordance with the setup resolution of the selection data, for example, when image information is input, or can also be provided by performing resolution conversion processing. For example, resolution can be set in response to user""s specification of the image quality or the image type. For example, if high picture quality is specified or the image type is specified as text, the selection data having text form information is set to high resolution, whereby text or a line drawing can be transmitted or stored with high image quality. If the user specifies the image type as picture such as photo, the first piece of image data having picture information is set to high resolution, whereby a picture can be transmitted or stored with high image quality.
Resolution can also be set considering the reception capability of a receiving system for receiving image information in the multilayer data format. For example, resolution can be determined based on the highest resolution at which the receiving system can receive image information; waste of the transmission time by transmitting image information at high resolution that cannot be handled at the receiving party can be avoided. The resolution of the selection data can be set to 1/ns the highest resolution at which the receiving system can receive image information where ns is a natural number, and the resolutions of the first piece of image data and the second piece of image data can be set to 1/n1 and 1/n2 the resolution of the selection data where n1 and n2 are each a natural number, whereby resolution conversion processing can be simplified and reconstructing the image in the receiving system is facilitated.
Further, resolution can also be set in response to the data amount. For example, if the compressed data amounts of the first piece of image data and the second piece of image data compressed are greater than predetermined amounts or the sum of the compressed data amounts is greater than a predetermined amount, the data is converted into lower resolution, the data amount is reduced, and the data can be again compressed, whereby the image information can be transmitted or stored in any desired data amount range.